Hemoglobin Lincoln Park: a betadelta fusion (anti-Lepore) variant with an amino acid deletion in the delta chain-derived segment.

An electrophoretically slow-moving hemoglobin variant was identified in three members of a family originating from Southern Mexico. The variant, Hb Lincoln Park, made up approximately 14% of the total hemoglobin and appeared to have normal stability and functional properties. None of the individuals in whom the abnormal hemoglobin was present was anemic, but each had a mildly elevated reticulocyte count. Structural data suggest that the non-alpha chain of Hb Lincoln Park represents a betadelta gene-fusion product, with normal beta chain structure of the amino-terminal portion of the chain and delta sequences subsequently, the crossover point occurring between animo acid residues 22 and 50. An additional abnormality is the deletion of valine-137, a component of the delta gene-derived segment of the betadelta chain. To account for the development of this abnormal globin chain, a series of intergenic crossovers is proposed; the first, a nonhomologous crossover between the beta and delta genes, presumably gave rise to the betadelta fusion gene; two additional crossovers, one of them unequal, may then have occurred between the same beta and delta genes to produce the amino acid deletion.